Two-dimensional semiconductors (2DSCs) have attracted considerable attention as atomically thin channel materials for field-effect transistors. Each layer in 2DSCs consists of a single- or few-atom-thick, covalently bonded lattice, in which all carriers are confined in their atomically thin channel with superior gate controllability and greatly suppressed OFF-state current, in contrast to typical bulk semiconductors plagued by short channel effects and heat generation from static power. Additionally, 2DSCs are free of surface dangling bonds that plague traditional semiconductors, and hence exhibit excellent electronic properties at the limit of single atom thickness...

Two-dimensional materials with intrinsic magnetism have recently drawn intense interest for both the fundamental studies and potential technological applications. However, the studies to date have been largely limited to mechanically exfoliated materials. Herein, an atmospheric pressure chemical vapor deposition route to ultrathin group VB metal telluride MTe2 (M = V, Nb, Ta) nanoplates with thickness as thin as 3 nm is reported. It is shown that the resulting nanoplates can be systematically evolved from mostly thicker hexagonal domains to thinner triangular domains with an increasing flow rate of the carrier gas...

Graphene-supported single atomic metals (G-SAMs) have recently attracted considerable research interest for their intriguing catalytic, electronic, and magnetic properties. The development of effective synthetic methodologies toward G-SAMs with monodispersed metal atoms is vital for exploring their fundamental properties and potential applications. A convenient, rapid, and general strategy to synthesize a series of monodispersed atomic transition metals (for example, Co, Ni, Cu) embedded in nitrogen-doped graphene by two-second microwave (MW) heating the mixture of amine-functionalized graphene oxide and metal salts is reported here...

Optical frequency combs, which emit pulses of light at discrete, equally spaced frequencies, are cornerstones of modern-day frequency metrology, precision spectroscopy, astronomical observations, ultrafast optics and quantum information1-7 . Chip-scale frequency combs, based on the Kerr and Raman nonlinearities in monolithic microresonators with ultrahigh quality factors8-10 , have recently led to progress in optical clockwork and observations of temporal cavity solitons11-14 . But the chromatic dispersion within a laser cavity, which determines the comb formation15,16 , is usually difficult to tune with an electric field, whether in microcavities or fibre cavities...

The development of future sustainable energy technologies relies critically on our understanding of electrocatalytic reactions occurring at the electrode-electrolyte interfaces, and the identification of key reaction promoters and inhibitors. Here we present a systematic in situ nanoelectronic measurement of anionic surface adsorptions (sulfates, halides, and cyanides) on ultrathin platinum nanowires during active electrochemical processes, probing their competitive adsorption behavior with oxygenated species and correlating them to the electrokinetics of the oxygen reduction reaction (ORR)...

The recent discovery of topological semimetals has stimulated extensive research interest due to their unique electronic properties and novel transport properties related to a chiral anomaly. However, the studies to date are largely limited to bulk crystals and exfoliated flakes. Here, we report the controllable synthesis of ultrathin two-dimensional (2D) platinum telluride (PtTe2 ) nanosheets with tunable thickness and investigate the thickness-dependent electronic properties. We show that PtTe2 nanosheets can be readily grown, using a chemical vapor deposition approach, with a hexagonal or triangular geometry and a lateral dimension of up to 80 μm, and the thickness of the nanosheets can be systematically tailored from over 20 to 1...

The junctions formed at the contact between metallic electrodes and semiconductor materials are crucial components of electronic and optoelectronic devices 1 . Metal-semiconductor junctions are characterized by an energy barrier known as the Schottky barrier, whose height can, in the ideal case, be predicted by the Schottky-Mott rule2-4 on the basis of the relative alignment of energy levels. Such ideal physics has rarely been experimentally realized, however, because of the inevitable chemical disorder and Fermi-level pinning at typical metal-semiconductor interfaces2,5-12 ...

Distinguishing structural isomers at the single-molecule level remains a challenge. We report the single-molecule recognition of two diketopyrrolopyrrole containing isomers (SDPP and SPPO) employing the mechanically controllable break junction technique. The single-molecule conductances of the two isomers are indistinguishable under normal conditions. However, reversible protonation and deprotonation of the SPPO in molecular junction result in more than 1 order of magnitude conductance change, which dramatically enhances the conductance difference between the two isomers...

Atomic substitution offers an important route to achieve compositionally engineered two-dimensional nanostructures and their heterostructures. Despite the recent research progress, the fundamental understanding of the reaction mechanism has still remained unclear. Here, we reveal the atomic substitution mechanism of two-dimensional atomic layered materials. We found that the atomic substitution process depends on the varying lattice constant (strain) in monolayer crystals, dominated by two strain-tuning (self-promoted and self-limited) mechanisms using density functional theory calculations...

The family of 2D semiconductors (2DSCs) has grown rapidly since the first isolation of graphene. The emergence of each 2DSC material brings considerable excitement for its unique electrical, optical, and mechanical properties, which are often highly distinct from their 3D counterparts. To date, studies of 2DSC are majorly focused on group IV (e.g., graphene, silicene), group V (e.g., phosphorene), or group VIB compounds (transition metal dichalcogenides, TMD), and have inspired considerable effort in searching for novel 2DSCs...

In the version of this Article originally published, Liban M. A. Saleh was incorrectly listed as Liban A. M. Saleh due to a technical error. This has now been amended in all online versions of the Article.

Two-dimensional atomic crystals (2DACs) have attracted intense recent interest. With a nearly perfect crystalline structure and dangling-bond free surface, these atomically thin materials have emerged as a new material platform for fundamental materials science and diverse technology opportunities at the limit of single atom thickness. Over the past decade, a wide range of 2DACs has been prepared by mechanically exfoliating bulk layered crystals, which has fueled the rapid progress of the entire field in terms of fundamental physics and basic device demonstrations...

There is significant interest in the development of methods to create hybrid materials that transform capabilities, in particular for Earth-abundant metal oxides, such as TiO2 , to give improved or new properties relevant to a broad spectrum of applications. Here we introduce an approach we refer to as 'molecular cross-linking', whereby a hybrid molecular boron oxide material is formed from polyhedral boron-cluster precursors of the type [B12 (OH)12 ]2- . This new approach is enabled by the inherent robustness of the boron-cluster molecular building block, which is compatible with the harsh thermal and oxidizing conditions that are necessary for the synthesis of many metal oxides...

High-quality two-dimensional atomic layered p-n heterostructures are essential for high-performance integrated optoelectronics. The studies to date have been largely limited to exfoliated and restacked flakes, and the controlled growth of such heterostructures remains a significant challenge. Here we report the direct van der Waals epitaxial growth of large-scale WSe2 /SnS2 vertical bilayer p-n junctions on SiO2 /Si substrates, with the lateral sizes reaching up to millimeter scale. Multi-electrode field-effect transistors have been integrated on a single heterostructure bilayer...

Silver nanowire (Ag-NW) thin films have emerged as a promising next-generation transparent electrode. However, the current Ag-NW thin films are often plagued by high NW-NW contact resistance and poor long-term stability, which can be largely attributed to the ill-defined polyvinylpyrrolidone (PVP) surface ligands and nonideal Ag-PVP-Ag contact at NW-NW junctions. Herein, we report a room temperature direct welding and chemical protection strategy to greatly improve the conductivity and stability of the Ag-NW thin films...

Negative transconductance (NTC) devices have been heavily investigated for their potential in low power logical circuit, memory, oscillating, and high-speed switching applications. Previous NTC devices are largely attributed to two working mechanisms: quantum mechanical tunneling, and mobility degradation at high electrical field. Herein we report a systematic investigation of charge transport in multilayer two-dimensional semiconductors (2DSCs) with optimized van der Waals contact and for the first time demonstrate NTC and antibipolar characteristics in multilayer 2DSCs (such as MoS2, WSe2)...

Two-dimensional layered materials (2DLMs) have attracted considerable recent interest as a new material platform for fundamental materials science and potential new technologies. Here we report the growth of layered metal halide materials and their optoelectronic properties. BiI3 nanoplates can be readily grown on SiO2 /Si substrates with a hexagonal geometry, with a thickness in the range of 10-120 nm and a lateral dimension of 3-10 µm. Transmission electron microscopy and electron diffraction studies demonstrate that the individual nanoplates are high quality single crystals...